Method and apparatus for operating a starter for an internal combustion engine

Abstract

A starter for an internal combustion engine includes a multi-phase brushless electric motor, a controller and an inverter. A method for controlling the starter includes determining initial current commands for operating the electric motor in response to an activation command. Electrical current supplied to the electric motor and a rotational position of an output member of the electric motor are monitored. The electrical current is monitored directly without an intervening current prediction step. Interim voltage commands are determined based upon the initial current commands and the monitored currents, and final voltage commands are determined by subjecting the interim voltage commands to voltage limits. A rotational position compensation term is determined based upon the rotational position and rotational speed of the electric motor, and operation of the inverter is controlled to control the electric motor based upon the final voltage commands and the rotational position compensation term.

What is claimed is: 
     
       1. A method for controlling a starter that is disposed on an internal combustion engine, the starter including a multi-phase electric motor, a controller and an inverter, the method comprising:
 determining initial current commands for operating the electric motor in response to an activation command, wherein the activation command includes a rotational speed command concurrent with a motor torque command; 
 determining electrical current transferred from a DC power source to the electric motor and a rotational position of an output member of the electric motor, wherein the electrical current is determined directly without an intervening current prediction step; 
 determining feedback currents from the electric motor based upon the electrical current transferred to the electric motor and the rotational position; 
 determining interim voltage commands based upon the initial current commands and the feedback currents; 
 subjecting the interim voltage commands to voltage limits to determine final voltage commands; 
 determining a position compensation term based upon the rotational position and a rotational speed of the electric motor; and 
 controlling, via the controller, operation of the inverter in a pulse width-modulated mode to control the electric motor based upon the final voltage commands and the position compensation term. 
 
     
     
       2. The method of  claim 1 , wherein the activation command comprises a command to start the internal combustion engine, and wherein the initial current commands for operating the electric motor are determined in response to the rotational speed command and the motor torque command associated with the activation command. 
     
     
       3. The method of  claim 1 , wherein determining the interim voltage commands based upon the initial current commands and the feedback currents comprises determining, via a decoupled current controller element, the interim voltage commands based upon the initial current commands and the feedback currents. 
     
     
       4. The method of  claim 1 , wherein determining the interim voltage commands based upon the initial current commands and the feedback currents further comprises employing a proportional/integrator control routine to determine the interim voltage commands, wherein the integrator is subjected to a dynamic integrator clamping element and an anti-windup element from a gain saturation limiter. 
     
     
       5. The method of  claim 1 , further comprising:
 wherein the interim voltage commands include space-vector voltage commands including a d-axis interim voltage command and a q-axis interim voltage command, 
 wherein the dynamic integrator clamping element includes a d-scale voltage limit and a q-scale voltage limit, and 
 wherein the d-scale voltage limit is determined based upon the interim d-axis voltage command and a system voltage; 
 wherein the q-scale voltage limit is determined based upon the interim q-axis voltage command and the system voltage; 
 wherein the d-axis interim voltage command is dynamically subjected to the d-scale voltage limit; and 
 wherein the q-axis interim voltage command is dynamically subjected to the q-scale voltage limit. 
 
     
     
       6. The method of  claim 1 , further comprising, monitoring, via sensors, electrical current transferred to the electric motor and the rotational position of the output member of the electric motor. 
     
     
       7. A method for controlling a starter that is disposed on an internal combustion engine, the starter including a multi-phase brushless electric motor coupled to a rotatable pinion gear, a controller and an inverter, the method comprising:
 determining initial current commands for operating the electric motor in response to an activation command, wherein the activation command includes a rotational speed command concurrent with a motor torque command; 
 monitoring, via current sensors, electrical current transferred from a DC power source to the electric motor, wherein the electrical current is monitored directly without an intervening current prediction step; 
 monitoring, via a rotational position sensor, a rotational position of the pinion gear; 
 determining feedback currents from the electric motor based upon the electrical current transferred to the electric motor and the rotational position of the pinion gear; 
 determining interim voltage commands based upon the initial current commands and the feedback currents, including employing a proportional/integrator control routine to determine the interim voltage commands, wherein the integrator is subjected to a dynamic integrator clamping element and an anti-windup element from a gain saturation limiter; 
 subjecting the interim voltage commands to voltage limits to determine final voltage commands; 
 determining a rotational position compensation term based upon the rotational position of the pinion gear and a rotational speed of the electric motor; 
 determining pulse width-modulated commands for controlling the inverter based upon the final voltage commands and the rotational position compensation term; and 
 controlling, via the controller, operation of the inverter to control the electric motor based upon the pulse width-modulated commands. 
 
     
     
       8. The method of  claim 7 , wherein the activation command comprises a command to start the internal combustion engine, and wherein the initial current commands for operating the electric motor are determined in response to the rotational speed command and the motor torque command associated with the activation command. 
     
     
       9. The method of  claim 7 , wherein determining the interim voltage commands based upon the initial current commands and the feedback currents comprises determining, via a decoupled current controller element, the interim voltage commands based upon the initial current commands and the feedback currents. 
     
     
       10. The method of  claim 7 , further comprising:
 wherein the interim voltage commands comprise space-vector voltage commands including a d-axis interim voltage command and a q-axis interim voltage command, 
 wherein the dynamic integrator clamping element includes a d-scale voltage limit and a q-scale voltage limit, and 
 wherein the d-scale voltage limit is determined based upon the interim d-axis voltage command and a system voltage; 
 wherein the q-scale voltage limit is determined based upon the interim q-axis voltage command and the system voltage; 
 wherein the d-axis interim voltage command is dynamically subjected to the d-scale voltage limit; and 
 wherein the q-axis interim voltage command is dynamically subjected to the q-scale voltage limit. 
 
     
     
       11. The method of  claim 7 , further comprising, monitoring, via sensors, electrical current transferred to the electric motor and a rotational position of the pinion gear. 
     
     
       12. A starter disposed on an internal combustion engine, comprising:
 a multi-phase brushless electric motor coupled to a rotatable pinion gear, a controller, a DC power source, and an inverter, the controller operatively connected to the inverter, the controller including an instruction set, the instruction set executable to:
 determine initial current commands to operate the electric motor in response to an activation command, wherein the activation command includes a rotational speed command concurrent with a motor torque command; 
 monitor electrical current transferred to the electric motor from the DC power source, and a rotational position of the pinion gear; 
 determine feedback current commands for the electric motor based upon the electrical current transferred to the electric motor and the rotational position of the pinion gear; 
 determine interim voltage commands based upon the initial current commands and the feedback currents, including employing a proportional/integrator control routine to determine the interim voltage commands, wherein the integrator is subjected to a dynamic integrator clamping element and an anti-windup element from a gain saturation limiter; 
 subject the interim voltage commands to voltage limits to determine final voltage commands; 
 determine a rotational position compensation term based upon the rotational position of the pinion gear and a rotational speed of the electric motor; and 
 control operation of the inverter in a pulse width-modulated mode to control the electric motor based upon the final voltage commands and the rotational position compensation term. 
 
 
     
     
       13. The starter of  claim 12 , further comprising, monitoring, via sensors, electrical current transferred to the electric motor and a rotational position of the pinion gear. 
     
     
       14. The method of  claim 1 , wherein the position compensation element is determined based upon the rotational speed of the electric motor and a theoretical position delay due to sampling of the rotational position of the electric motor. 
     
     
       15. The method of  claim 7 , wherein the position compensation element is determined based upon the rotational speed of the electric motor and a theoretical position delay due to sampling of the rotational position of the electric motor. 
     
     
       16. The starter of  claim 12 , wherein the rotational position compensation element is determined based upon the rotational speed of the electric motor and a theoretical position delay due to sampling of the rotational position of the electric motor.